This story was updated at 1:07 p.m. EDT.
CAPE CANAVERAL, Fla. - A mild toxic leak and a smoke-like smell aboard the International Space Station (ISS) prompted an afternoon scare for three astronauts aboard the orbital laboratory, mission managers said Monday.
The station's three-astronaut Expedition 13 crew reported a smoke-like smell in the laboratory's Russian-built Zvezda service module and initially reported smoke itself, though the emergency was later traced to a toxic irritant leak used in a primary oxygen generator.
"Everything is good, everything is fine," Expedition 13 commander Pavel Vinogradov told Russian ISS mission controllers in Moscow, adding that he had contained the apparent leak in a rubber bag. "There is no more discharge, no more liquid."
"The situation is stable right now," Expedition 13 flight engineer Jeffrey Williams told Mission Control as he worked through the issue during the station's afternoon shift. "There's an obvious smell. There was never any smoke."
In addition to Vinogradov - of Russia's Federal Space Agency - and NASA's Williams, flight engineer Thomas Reiter of the European Space Agency live aboard the ISS.
The crew tracked the smell to a leak in the station's Russian-built Elektron oxygen generator, which separates water into hydrogen and oxygen through electrolysis, early Monday and shut down the unit at about 7:02 a.m. EDT (1102 GMT), NASA officials said. It was later when Williams clarified his report, adding that no smoke was immediately apparent.
"We have some sort of a leak, we don't understand the source yet, but some sort of a leak of potassium hydroxide (KOH), that's coming out of the [oxygen] vent," NASA ISS program manager Michael Suffredini said in a briefing, adding that the liquid is classified as a "Tox 2" irritant aboard the station. "It's not a life-threatening material."
But the crew's initial report of smoke prompted NASA and Russian ISS mission managers to declare a spacecraft emergency to gain access to communications satellites during the short-lived crisis, Suffredini said, adding that all ventilation systems shut down aboard the ISS to prevent the odor from spreading.
At no point did NASA or Russian ISS mission controllers consider sending the Expedition 13 crew to their Soyuz lifeboat for either shelter or an emergency undocking, Suffredini said.
NASA spokesperson John Ira Petty told SPACE.com that the carbon dioxide levels inside the station's Russian segment were low enough that the crew did not have to don their emergency gas masks.
But the astronauts did have to wear gloves and surgical masks to avoid irritation from the potassium hydroxide, NASA officials said.
The incident should not affect the Sept. 20 docking of a new Soyuz TMA-9 spacecraft carrying the Expedition 14 relief crew for Vinogradov and Williams, as well as paying ISS visitor Anousheh Ansari. The trio launched at 12:09 a.m. EDT (0409 GMT) Monday.
"There's no reason right now that I know of that we would not have the crew come in and do the crew change-out," Suffredini said. "In fact, with the extra crew there, it might be a good time to do any troubleshooting and [replace and repair] work we think we need to do."
NASA's space shuttle Atlantis and its six-astronaut STS-115 crew undocked from the ISS Sunday after a week of spacewalks and orbital construction to deliver the $372 million Port 3/Port 4 trusses and solar arrays to the station.
Space station crews have had difficulties with the station's Elektron unit in the past, but the current unit has experienced none of those glitches, Suffredini said, adding that the ISS also has plenty of oxygen supplies aboard its current Progress 22 supply ship and in storage tanks aboard the station itself.
A spare Elektron unit is onboard, and would require between one or two days to install if ISS managers decide it is necessary. Another option is to repair parts of the Elektron system.
"It's about the size of a water heater," Suffredini said of the Elektron.
ISS flight controllers told Williams that potassium hydroxide is typically odorless, and that the source of the alarming smell may be due to a rubber gasket that Vinogradov reported as damaged by apparent overheating in the Elektron unit.
"I believe that the rubber seal produced that odor," Vinogradov said, adding that the Elektron appeared to stop leaking after he shut it off.
While Williams reported no smoke in the space station's main cabin, that gasket itself was seen to be visibly smoking upon inspection, he told NASA astronaut Shannon Lucid, serving as ISS spacecraft communicator at Johnson Space Center in Houston later.
There were reports of the odor all the way in the U.S.-built Destiny laboratory on the opposite end of the ISS from the smell's source in the Zvezda module, Suffredini added. Russia's Zarya control module and the NASA's Unity node bridge Destiny and Zvezda together.
By 9:05 a.m. EDT (1505 GMT), the smoke-like smell had dwindled and life aboard the ISS returned to near normal operating conditions. It should take about 36 hours to completely swap and scrub the station's entire atmosphere, space station officials said.
"The smell has gone," Williams told Lucid. "It has decreased significantly."
Vinogradov reported a series of up to five drops leaked out of the Elektron before it was shut down, followed by large, three-centimeter globules, all of which he contained in a rubber bag. The liquid was clear, "like water," Vinogradov said.
The liquid will be discarded in October aboard the Progress 22. An earlier supply ship, Progress 21, will be jettisoned from its berth at the aft end of the station's Zvezda module later today and has already been sealed for undocking, Suffredini said.
In 2002, ISS astronauts were confined to the Russian segment of the station due to a glitch with the outpost's U.S.-built Quest airlock. The odor prompted headaches in the station's three Expedition Four astronauts.
Higher than normal concentrations of carbon dioxide in the station's Zarya control module may also have contributed to some ill effects reported by NASA's STS-96 astronaut crew in 1999.
ISS astronauts are trained to respond to several types of emergency - both before flight and while in orbit - including smoke and fires, toxic leaks and rapid decompression, Suffredini said. Aboard the ISS, station crews hold a monthly fire drill, he added.
Williams later asked flight controllers to contact the Expedition 13 crew's families to let them know what had occurred.
"Jeff, we're already working on that and we're calling Anna-Marie," Lucid told him, referring to Williams' wife.
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